Methods for determining and controlling battery expansion

ABSTRACT

Methods and systems for detecting and compensating for expansion of rechargeable batteries over time. An expansion detector may be coupled to or positioned proximate a rechargeable battery to monitor for expansion thereof. After expansion exceeding a selected threshold is detected, the expansion detector may report the expansion to an associated processing unit. The processing unit may undertake to arrest further rechargeable battery expansion by modifying or changing one or more characteristics of charging and/or discharging circuitry coupled to the rechargeable battery. For example, the processing unit may charge the rechargeable battery at a lower rate or with reduced voltage after detecting expansion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a nonprovisional patent application of and claimsthe benefit to U.S. Provisional Patent Application No. 62/043,263, filedAug. 28, 2014 and titled “Methods for Determinging and ControllingBattery Expansion,” the disclosure of which is hereby incorporatedherein in its entirety.

TECHNICAL FIELD

Embodiments described herein relate to battery charging systems, andmore particularly, to systems and methods for determining andcontrolling expansion of rechargeable batteries over time.

BACKGROUND

Portable electronic devices may include one or more batteries that mayrequire recharging from time to time. Such devices may include electricvehicles, cell phones, smart phones, tablet computers, laptop computers,wearable devices, navigation devices, sports devices, health analysisdevices, medical data devices, location tracking devices, accessorydevices, home appliances, peripheral input devices, remote controldevices, and so on. As a result of high packing density, high energydensity, long cycle life, and ease of mass production, portableelectronic devices typically include one or more lithium-polymer orlithium-ion batteries.

Over the operational life of a lithium-polymer rechargeable battery, theinternal resistance of the rechargeable battery may increase as a resultof oxidation, lithium dendrite growth, cathodic gas evolution, and/orcathodic degradation, due at least in part to repeated charging anddischarging of the rechargeable battery. As a result, the power outputcapacity of the rechargeable battery may decrease over time, undesirablylimiting the useful life of the rechargeable battery and/or the portableelectronic device. In other examples, non-optimal charging conditionscan also effect an increase in internal resistance of the rechargeablebattery. For example, the internal resistance of the battery mayincrease as a result of charging at high voltage, delayed transitionfrom constant current to constant voltage charging, and/or charging ordischarging at a high temperature. In many examples, the internalresistance of the rechargeable battery may correlate or correspond totarget charge capacity, rechargeable battery health, and/or rechargeablebattery age.

In addition, lithium-polymer batteries may physically expand or swellduring charging of the rechargeable battery. For example, the anodematerial can expand substantially over repeated charging cycles or evenduring a single charging cycle. In other cases, gas emissions from acharged cathode can, over time, result in an expanded rechargeablebattery. Over time, the rechargeable battery can expand beyond itsallotted volume within the portable electronic device, damagingcomponents and/or portions the portable electronic device. In thesecases, a user of a portable electronic device may be entirely unaware ofthe expansion of the rechargeable battery until conspicuous physicaldamage occurs.

Accordingly, there may be a present need for a method and system fordetecting, arresting, mitigating, and compensating for rechargeablebattery expansion.

SUMMARY

Embodiments descried herein may relate to, include, or take the form ofmethods and systems for detecting and compensating for rechargeablebattery expansion over time.

For example, certain embodiments described herein may take the form ofan electronic device including at least a housing, a rechargeablebattery within the housing, a processing unit configured to control theelectrical input received from a power source coupled to therechargeable battery, and an expansion detector electrically coupled tothe processing unit. In these embodiments, the expansion detector cansend an expansion signal to the processing unit upon determining thatthe rechargeable battery has expanded, and in response to receiving theexpansion signal, the processing unit can modify one or morecharacteristics of the electrical input. For example, the processingunit may modify the output voltage, current, or scheduling of theelectrical input.

In certain embodiments, the expansion detector may be any suitablesensor or detector configured to detect dimensional expansion of therechargeable battery. For example, in certain embodiments the expansiondetector may be a capacitive sensor. The capacitive sensor can measurefor changes in capacitance between two or more electrically conductivesurfaces. In certain embodiments, at least one of the surfaces may be asurface of the rechargeable battery. In one example, a second surfacemay be a surface of the housing of the electronic device. Upon expansionof the rechargeable battery, the distance between the first and secondsurface may change and according, the capacitance between the first andsecond surface can change. In this manner, the capacitive sensor maydetermine that the rechargeable battery has expanded.

In other examples the capacitive sensor can be positioned elsewhere todetect a dimensional expansion of the rechargeable battery. For example,one electrically conductive plate may be positioned on a top surface ofthe rechargeable battery and another electrically conductive plate maybe positioned on a bottom surface of the rechargeable battery. Infurther examples, one electrically conductive plate may be positionedwithin the rechargeable battery and another electrically conductiveplate may be positioned outside the rechargeable battery. In otherexamples, the capacitive sensor may be pixelized in order to determineexpansion of the rechargeable battery at more than one location.

Other embodiments may include a configuration in which the expansiondetector includes a strain sensor coupled to an external surface of therechargeable battery, a resistance sensor coupled to an external surfaceof the rechargeable battery, an acoustic resonance sensor, a photointerrupter positioned across the rechargeable battery, a contactswitch, or a pressure sensor. Each of these example expansion detectorsmay send an expansion signal to the processing unit upon determiningthat the rechargeable battery has expanded beyond a selected threshold.

Other embodiments described herein may relate to, include, or take theform of a rechargeable battery within the housing of a portableelectronic device, the rechargeable battery including at least arechargeable battery module, a pouch containing the rechargeable batterymodule, and a rechargeable battery expansion detector electricallycoupled to a processing unit associated with the portable electronicdevice. In these embodiments, the expansion detector can send anexpansion signal to the processing unit upon determining that therechargeable battery has expanded, and in response to receiving theexpansion signal, the processing unit can modify one or morecharacteristics of the electrical input, such as the output voltage,current, or scheduling of the electrical input.

These embodiments may include a configuration in which the expansiondetector includes a capacitive sensor, a strain sensor coupled to anexternal surface of the rechargeable battery, a resistance sensorcoupled to an external surface of the rechargeable battery, an acousticresonance sensor, a photo interrupter positioned across the rechargeablebattery, a contact switch, or a pressure sensor. Each of these exampleexpansion detectors may send an expansion signal to the processing unitupon determining that the rechargeable battery has expanded beyond aselected threshold.

Certain embodiments described herein may also relate to, include, ortake the form of a method for adjusting power output from a power supplyconfigured to charge a rechargeable battery, the method including atleast the operations of determining whether the rechargeable battery hasexpanded beyond a selected threshold, and changing one or more poweroutput characteristics of the power supply in response to determiningthat the selected threshold may be exceeded. For example, the outputvoltage, current, or scheduling of the electrical input and/or powersource may be changed in response to determining that the rechargeablebattery has expanded.

Additional embodiments described herein may also relate to, include, ortake the form of a method for adjusting power output from a power supplyconfigured to charge a rechargeable battery, the method including atleast the operations of determining whether the output power presents arisk of rechargeable battery expansion, determining whether the risk ofrechargeable battery expansion exceeds a selected threshold, andchanging one or more power output characteristics of the power supply inresponse to determining that the selected threshold may be exceeded. Forexample, the output voltage, current, or scheduling of the electricalinput and/or power source may be changed in response to determining thatthe rechargeable battery has expanded.

These embodiments may determine an increased risk of rechargeablebattery expansion by, for example, determining whether the age of therechargeable battery exceeds a selected age, determining whether thecharge/discharge cycle count of the rechargeable battery exceeds aselected maximum, determining whether the temperature of therechargeable battery exceeds a selected temperature threshold,determining whether the rate of expansion exceeds a selected ratethreshold, or determining whether the internal resistance of therechargeable battery exceeds a selected resistances threshold.

BRIEF DESCRIPTION OF THE FIGURES

Reference will now be made to representative embodiments illustrated inthe accompanying figures. It should be understood that the followingdescriptions are not intended to limit the disclosure to one preferredembodiment. To the contrary, the following descriptions are intended tocover alternatives, modifications, and equivalents as may be includedwithin the spirit and scope of the described embodiments as defined bythe appended claims.

FIG. 1 depicts an example front view of a portable electronic devicethat may include one or more internal rechargeable batteries.

FIG. 2A depicts an example top plan view of a rechargeable battery.

FIG. 2B depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and anexpansion detector in an unexpanded state.

FIG. 2C depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and anexpansion detector in an expanded state.

FIG. 2D depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and analternate expansion detector in an unexpanded state.

FIG. 2E depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and analternate expansion detector in an unexpanded state.

FIG. 2F depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and analternate expansion detector in an unexpanded state.

FIG. 2G depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and analternate expansion detector in an unexpanded state.

FIG. 2H depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and analternate expansion detector in an unexpanded state.

FIG. 2I depicts a cross-section taken along line 2B-2B of therechargeable battery of FIG. 2A, showing the rechargeable battery and analternate expansion detector in an unexpanded.

FIG. 3 depicts an example side cross-section of an example rechargeablebattery and a pixelized expansion detector.

FIG. 4 depicts another example side cross-section of an examplerechargeable battery and an expansion detector disposed within ahousing.

FIG. 5 depicts an example side cross-section of an example rechargeablebattery and an expansion detector disposed within a housing.

FIG. 6A depicts an example top plan view of an example rechargeablebattery and an expansion detector disposed on an exterior surface of therechargeable battery, showing the rechargeable battery in an unexpandedstate.

FIG. 6B depicts an example top plan view of an example rechargeablebattery and an expansion detector disposed on an exterior surface of therechargeable battery, showing the rechargeable battery in an expandedstate.

FIG. 6C depicts an example top plan view of an example rechargeablebattery and another expansion detector disposed on an exterior surfaceof the rechargeable battery, showing the rechargeable battery in anunexpanded state.

FIG. 6D depicts an example top plan view of an example rechargeablebattery and another expansion detector disposed on an exterior surfaceof the rechargeable battery, showing the rechargeable battery in anunexpanded state.

FIG. 6E depicts an example top plan view of the expansion detector ofFIG. 6D disposed on an exterior surface of the rechargeable battery,showing the rechargeable battery in an expanded state.

FIG. 7 is a flow chart depicting example operations of a method fordetecting rechargeable battery expansion that exceeds a selectedthreshold.

FIG. 8 is a flow chart depicting example operations of a method forcompensating for and arresting rechargeable battery expansion.

FIG. 9 is another flow chart depicting example operations of a methodfor predicting and/or inferring rechargeable battery expansion as aresult of rechargeable battery age.

FIG. 10 is another flow chart depicting example operations of a methodfor mitigating rechargeable battery expansion over time.

FIG. 11 is another flow chart depicting example operations of a methodfor predicting and or inferring rechargeable battery expansion as aresult of rechargeable battery age.

The use of the same or similar reference numerals in different drawingsindicates similar, related, or identical items.

DETAILED DESCRIPTION

Many embodiments described herein may relate to methods and systems fordetecting, arresting, mitigating and/or compensating for batteryexpansion over time, and in several cases with respect to rechargeablebatteries. Although many embodiments are described herein with referenceto batteries for use with portable electronic devices, it should beappreciated that some embodiments can take other forms and may beincluded within different form factors. Accordingly, it should beappreciated that the various embodiments described herein, as well asthe functionality, operation, components, and capabilities thereof maybe combined with other elements as necessary, and so any physical,functional, or operational discussion of an element or feature is notintended to be limited solely to a particular embodiment to theexclusion of others.

Certain embodiments may be suitable for inclusion within the housing ofa portable electronic device. For example, some embodiments include anexpansion detector configured to monitor battery expansion over the lifeof a rechargeable battery. After expansion beyond a selected thresholdis detected, the expansion detector may send a signal to a processingunit associated with the portable electronic device. In response toreceiving the expansion signal, the processing unit may adjust one ormore characteristics and/or settings of the charging or dischargingcontrol circuitry of the portable electronic device.

In one embodiment, if expansion is detected, the processing unit mayconfigure charging circuitry to reduce the voltage applied to charge therechargeable battery. In other examples, the processing unit may updatea function used to determine the appropriate voltage applied to chargethe rechargeable battery. For example, some embodiments may select thevoltage to charge a rechargeable battery as a function of rechargeablebattery age, rechargeable battery health, rechargeable batterytemperature, ambient temperature, and/or characteristics related to thecharger connected to the portable electronic device. Thus, certainembodiments may change the characteristic on which the voltage chargingfunction depends as the battery swells or contracts.

In these examples, if expansion is detected, the processing unit mayadjust the determined rechargeable battery age or the determinedrechargeable battery health (or other measured or calculated values) inorder to effect a change to the characteristics of the function thatdetermines the voltage applied to the rechargeable battery. Moreparticularly, in some embodiments, if expansion is detected, effectiverechargeable battery age may be increased and/or effective rechargeablebattery health may be decreased. Each of these adjustments may result ina reduction of the voltage applied to charge the rechargeable battery.Conversely, if the effective age or health of the rechargeable batteryis decreased, the voltage applied to charge the battery may beincreased.

In other examples, the processing unit may terminate charging ordischarging immediately if expansion is detecting in order to preventpermanent damage to the portable electronic device. For example incertain embodiments the expansion detector and/or processing unit maymonitor for rechargeable battery expansion rate in addition torechargeable battery expansion. In one example, a low rechargeablebattery expansion rate may be expected as a result of normal aging anduse of the rechargeable battery. In a second example, an acceleratedrechargeable battery expansion rate may indicate a rechargeable batteryfailure, manufacturing defect, premature mechanical or chemical failure,physical damage to the rechargeable battery, unsafe charging/dischargingconditions, use of third-party or otherwise unknown chargers, or anyother potentially unexpected circumstance. In these and relatedembodiments, the portable electronic device may respond differently todifferent rechargeable battery expansion rates. Continuing the example,the portable electronic device may adjust charging or dischargingconditions in response to the first detected rechargeable batteryexpansion rate whereas the portable electronic device may activelyterminate all power, may trigger one or more power protections circuits,and/or may trigger one or more sacrificial components to attempt toarrest the accelerated expansion of the rechargeable battery.

In still further examples, the portable electronic device may provide anotification of rechargeable battery expansion to a user or athird-party. For example, the third party may be a manufacturer of theportable electronic device or the rechargeable battery. The notificationmay provide the third party with usage statistics (either anonymized orspecific to a particular device or user). In another example, thenotification may inform a user or the third-party that the rechargeablebattery may be in need of reconditioning or replacement.

In certain embodiments, the expansion detector may be any suitablesensor or detector configured to detect dimensional expansion of therechargeable battery. For example, in certain embodiments the expansiondetector may be a capacitive sensor. The capacitive sensor can measurechanges in capacitance between two or more electrically conductivesurfaces. In these embodiments, the electrically conductive surfaces maybe positioned such that expansion of the rechargeable battery causes theplates to move closer together or farther apart. For example, in oneembodiment, capacitance changes between a top and bottom surface of therechargeable battery may be measured. Thus, increases in capacitance mayequate to swelling or other expansion of the battery, while decreases incapacitance indicate a contraction of the battery.

In many embodiments, one or more expansion detectors may send anexpansion signal to a processing unit upon determining that therechargeable battery has expanded beyond a selected threshold. In manyexamples, the processing unit may be associated with the portableelectronic device, although this is not required. For example, theprocessing unit receiving the expansion signal may be a processing unitadapted to control the charging and dissipation of the rechargeablebattery.

Upon receiving the expansion signal, the processing unit may undertaketo mitigate or arrest further expansion of the rechargeable battery. Forexample, in certain embodiments, the processing unit may, in response toreceiving the expansion signal, alter one or more characteristics of thecharging or discharging cycle of the rechargeable battery. For example,conventional lithium-ion and/or lithium polymer batteries may be chargedwith constant current until cell voltage reaches a selected maximum(e.g., 4.2 volts as one non-limiting example). Thereafter, therechargeable battery may be charged with constant current at theselected maximum. Accordingly, embodiments described herein mayconfigure the processing unit to reduce the maximum charge voltageapplied to charge the rechargeable battery by a certain selected amountin response to receiving an expansion signal.

In certain examples, the processing unit can reduce the maximum chargevoltage by an amount proportional to the expansion of the rechargeablebattery. For example, if the rechargeable battery is determined to haveexpanded by three percent, the maximum charge voltage may be reduced bythree percent or any other suitable proportional amount (e.g., a directproportional adjustment need not be used; some embodiments may vary thevoltage reduction according to a non-linear relationship between thevoltage and expansion or volume). In other examples, the maximum chargevoltage can be reduced in steps. For example, if the rechargeablebattery is determined to have expanded three percent, the maximum chargevoltage may be reduced by 50 mV as a non-limiting example. Upon furtherexpansion of the rechargeable battery, the maximum charge voltage may befurther reduced in increments of 50 mV (again, as a non-limitingexample)

In still further examples, the maximum charge voltage of therechargeable battery can be reduced in response to an age calculation ordetermination of the rechargeable battery. For example, if therechargeable battery is designed to be charged and discharged 1000times, the processing unit may expect the rechargeable battery life tobe half over after 500 charge/discharge cycles. In these embodiments,the maximum charge voltage of the rechargeable battery can be adjustedupon reaching a threshold charge/discharge count. For example, for every50 charge/discharge cycles, the maximum charge voltage of therechargeable battery may be reduced by 50 mV. Still further embodimentsmay increase the maximum charge voltage applied to a rechargeablebattery in response to a determination that the rechargeable battery hasa higher than expected capacity.

In other examples, battery age may be determined or approximated basedat least in part on the target charge capacity of the rechargeablebattery at a particular time. For example, the processing unit maycompare the target charge capacity of the rechargeable battery to thedesigned capacity of the rechargeable battery. More particularly, if arechargeable battery is designed to hold 1000 mAh but is measured aftersome time as having a target charge capacity of only 900 mAh, theprocessing unit may conclude that the rechargeable battery has lost tenpercent of its total capacity. In response to the determination that therechargeable battery has lost ten percent capacity, the maximum chargevoltage may be reduced.

In some examples, the processing unit may be a processing unitassociated with a portable electronic device. In other examples theprocessing unit instead may be a power management unit dedicated tocontrolling the power input to the rechargeable battery. In otherembodiments, the processing unit instead may be a power management unitcontained within the battery package itself. In still furtherembodiments, the processing unit may be associated with an externalpower supply such as a power adapter.

Accordingly, many embodiments described herein may detect rechargeablebattery expansion via an expansion detector and/or via direct orindirect measurements or estimations of battery age or health.Thereafter, charging and/or discharging characteristics such as maximumcharge voltage may be adjusted to mitigate further expansion or capacitydegradation over time. In this manner, the useful life of portableelectronic devices and/or rechargeable batteries associated therewithmay be extended.

FIG. 1 depicts an example front view of a portable electronic device 100which may include one or more rechargeable batteries 200. The sampleillustrated embodiment shows the portable electronic device 100 as acellular telephone, although this embodiment is not required. Portable,semi-portable, or stationary devices that can include rechargeablebatteries may include electric vehicles, tablet computers, laptopcomputers, wearable devices, navigation devices, sports devices, healthanalysis devices, medical data devices, location tracking devices,accessory devices, home appliances, peripheral input devices, remotecontrol devices, and so on.

The portable electronic device 100, such as depicted in FIG. 1, mayinclude a housing 102, one or more input buttons 104, 106, and a display108. In some examples, the display 108 may include sensors for receivingtouch and/or force input.

In many examples, the portable electronic device 100 may include aprocessing unit coupled with or in communication with a memory, one ormore communication interfaces, output devices such as speakers, and oneor more input devices such as buttons, dials, microphones, ortouch-based and/or force-based interfaces. The communicationinterface(s) can provide electronic communications between the portableelectronic device 100 and any external communication network, device, orplatform, such as but not limited to wireless interfaces, Bluetoothinterfaces, Near Field Communication interfaces, infrared interfaces,USB interfaces, Wi-Fi interfaces, TCP/IP interfaces, networkcommunications interfaces, or any conventional communication interfaces.The portable electronic device 100 may provide information regardingtime, health, statuses or externally connected or communicating devicesand/or software executing on such devices, messages, video, operatingcommands, and so forth (and may receive any of the foregoing from anexternal device), in addition to communications.

In many cases, the portable electronic device 100 may include therechargeable batteries 200 completely within the housing 102. Forexample, the rechargeable battery 200 may be manufactured or otherwisesealed entirely within the housing 102. In another example, therechargeable battery 200 may be accessible to a user by removing one ormore portions of the housing 102.

The rechargeable battery 200 may be selected from or any number ofsuitable or conventional rechargeable battery technologies. However, asnoted above, many rechargeable batteries may be subject to swelling orexpansion over the operational life of the rechargeable battery and/orgiven certain non-optimal charging or discharging conditions.

For example, repeated charging and discharging of the rechargeablebattery 200 may increase the risk that the rechargeable battery mayexpand. In other examples, charging the rechargeable battery 200 in hightemperature conditions may cause and/or accelerate expansion of therechargeable battery 200. In still further examples, the risk ofrechargeable battery expansion may increase with rechargeable batteryage and/or decreased rechargeable battery health.

Over time, the rechargeable battery 200 may expand beyond the volumeallotted for the rechargeable battery within the housing 102 of theportable electronic device 100 and, accordingly, may physically damagecomponents and/or portions of the housing 102 or the portable electronicdevice 100. For example, as depicted in FIG. 1, the display 108 may bedamaged as a result of the expansion of the rechargeable battery 200.

Accordingly, many embodiments described herein relate to and take theform of methods to detect, arrest, and/or prevent expansion of therechargeable battery 200 over the operational life of the portableelectronic device 100. Many embodiments include one or more expansiondetectors 206 that are configured and adapted to detect the expansion ofthe rechargeable battery 200. After an expansion of the rechargeablebattery 200 is detected, the portable electronic device 100 can adjusthow the rechargeable battery 200 is charged and/or discharged.

For example, in one embodiment, the portable electronic device 100 maycharge the rechargeable battery 200 at a lower rate if an expansion ofthe rechargeable battery 200 is detected.

In another embodiment, the portable electronic device 100 may dischargethe rechargeable battery 200 at a lower rate if an expansion of therechargeable battery 200 is detected.

In another embodiment, the portable electronic device 100 may alert theuser or a third-party, for example by showing an alert on the display108 or by sending a message via one or more communication channels, ifan expansion of the rechargeable battery 200 is detected.

In another example, the portable electronic device 100 may lower amaximum charging temperature threshold of the rechargeable battery 200such that the rechargeable battery 200 is prevented from receiving powerwhen the rechargeable battery temperature and/or ambient temperatureexceeds the temperature threshold. If the rechargeable battery 200continues to expand, the portable electronic device may continue tolower the maximum charging temperature.

FIG. 2A depicts an example top plan view of a rechargeable battery 200.In one embodiment, the rechargeable battery 200 may be a lithium-polymerrechargeable battery, although this is not required, and otherrechargeable batteries or non-rechargeable batteries may be used inconjunction with or as elements of various systems and methods describedherein.

The rechargeable battery 200 may be made from one or more independentrechargeable battery cells contained within an external housing 202 suchas a flexible pouch. In many embodiments, each rechargeable battery cellcontained within the rechargeable battery 200 may be made from a numberof layers in a conventional jellyroll configuration. In these examples,the jellyroll configuration may include a cathode separated from ananode by a separator. The cathode and anode may be electrically coupledto two or more terminals 204.

FIG. 2B depicts a cross-section taken along line 2B-2B of therechargeable battery 200 of FIG. 2A, showing a simplified view of therechargeable battery and an expansion detector 206 in an unexpandedstate. The rechargeable battery 200 may be made from one or moreindependent rechargeable battery cells 204 contained within an externalhousing 202 such as a flexible pouch. The cells 204 may be arranged inthe aforementioned jellyroll configuration.

As with respect to other embodiments described herein, the expansiondetector 206 may be any suitable sensor or detector configured to detectdimensional expansion of the rechargeable battery. As illustrated, theexpansion detector may be a capacitive sensor constructed from two ormore electrically conductive surfaces 206 a, 260 b. The expansiondetector 206 can measure for changes in capacitance between two or moreelectrically conductive surfaces 206 a, 260 b, for example, resultingfrom separation of the electrically conductive surfaces 206 a, 260 b. Asillustrated a first electrically conductive surface 206 a may bedisposed or otherwise positioned on an upper surface or top surface ofthe external housing 202. In many embodiments, the first electricallyconductive surface 206 a may be positioned outside the housing, althoughthis is not required. For example, the first electrically conductivesurface 206 a may be positioned within the housing in certainembodiments.

A second electrically conductive surface 206 b may be disposed orotherwise positioned on a lower surface or a bottom surface of theexternal housing 202. Similar to the first electrically conductivesurface 206 a, the second electrically conductive surface 206 b may bepositioned outside the external housing 202, although this is notrequired.

In many examples the electrically conductive surfaces 206 a, 206 b maybe plates or structures of metal (such as copper, aluminum, and silver),ceramic, compositions such as indium-tin oxide and carbon nanotubes, orany other suitable electrically conductive material. In theseembodiments, the electrically conductive surfaces 206 a, 206 b may bemade from the same or different materials. In other examples, theelectrically conductive surfaces 206 a, 206 b may be adhered to theexternal housing 202 of the rechargeable battery 200 or a structurewithin the housing by any number of suitable methods. For example, anadhesive layer may be disposed between the electrically conductivesurfaces 206 a, 206 b and the external surfaces of the external housing202.

In certain examples, the electrically conductive surfaces 206 a, 206 bmay be disposed, printed, deposited, or otherwise manufactured onto therechargeable battery 200. For example, the electrically conductivesurfaces 206 a, 206 b may be electrically conductive layers of the pouchthat defines the external housing 202.

In these and related examples, the capacitance between the electricallyconductive surfaces 206 a, 206 b may be correlated to the distanceseparating the electrically conductive surfaces 206 a, 206 b. In otherwords, the difference between a baseline capacitance between theelectrically conductive surfaces 206 a, 206 b and a measured capacitancebetween electrically conductive surfaces 206 a, 206 b may correlate tothe amount or distance that the rechargeable battery 200 has expanded.For example, as shown in FIG. 2C, an expanded rechargeable battery mayresult in a physical separation of the electrically conductive surfaces206 a, 206 b. By periodically measuring or inferring the capacitancebetween the electrically conductive surfaces 206 a, 206 b, the expansionof the rechargeable battery 200 can be determined.

As noted above, the configuration of electrically conductive surfaces206 a, 206 b positioned on external and opposite surfaces of therechargeable battery is not required. For example, FIG. 2D depicts across-section taken along line 2B-2B of the rechargeable battery of FIG.2A, showing the rechargeable battery and an expansion detector 206 in anunexpanded state. In this example, the expansion detector 206 is madefrom the electrically conductive surfaces 206 a, 206 b separated by aninsulator 206 c. The material selected for the insulator 206 c may beselected, at least in part, based on dielectric properties. In thisexample, expansion of the rechargeable battery 200 may result in adeformation of the electrically conductive surfaces 206 a, 206 b suchthat the capacitance between the electrically conductive surfaces 206 a,206 b changes.

In other embodiments, the electrically conductive surfaces 206 a, 206 band the insulator 206 c may be positioned within the external housing202 of the rechargeable battery 200, for example as shown within FIG.2E. In other embodiments, the insulator 206 c may not be required. Forexample, as shown in FIG. 2F, one or more independent rechargeablebattery cells 204 may separate the electrically conductive surfaces 206a, 206 b. In still further embodiments, the electrically conductivesurfaces 206 a, 206 b may be separated, at least in part by a portion ofthe external housing 202 of the rechargeable battery 200, for example asshown in FIG. 2G. In still further examples, the electrically conductivesurfaces 206 a, 206 b may be separated by both a portion of the externalhousing 202 of the rechargeable battery 200 and a portion of the one ormore independent rechargeable battery cells 204.

In still further embodiments, one of either the electrically conductivesurfaces 206 a, 206 b may be physically coupled to a portion of thehousing 102 of the portable electronic device (not pictured) or astructure within the housing, for example as shown in FIG. 2I. One mayappreciate that the various configurations and layouts of theelectrically conductive surfaces 206 a, 206 b, as illustrated anddescribed with respect to FIGS. 2B-2H, may be modified or augmented toinclude one of the electrically conductive surfaces 206 a, 206 b oneither an internal or external surface of the housing of the portableelectronic device.

FIG. 3 depicts an example side cross-section of an example rechargeablebattery 300 and a pixelized expansion detector. As described withrespect to the embodiments illustrated in FIGS. 2A-2I, the pixelizedexpansion detector may be a capacitive sensor constructed from two ormore electrically conductive surfaces 306, 308. The electricallyconductive surface 308 may be formed into an array of independentelectrically conductive surfaces (e.g., pixelized). In this manner, theexpansion detector can measure changes in capacitance between each ofthe electrically conductive surfaces 308 in the array and theelectrically conductive surface 306. Due to the pixelation of theelectrically conductive surface 308, the expansion detector may besuitable for detecting expansion at various locations of therechargeable battery 300.

FIG. 4 depicts another example side cross-section of an examplerechargeable battery 400 and an expansion detector 408 disposed within ahousing. In certain embodiments, the expansion detector 408 may be aphoto interrupter positioned across the rechargeable battery, within acavity defined between an external surface of the rechargeable batteryand an internal surface of a housing 406. In certain embodiments thehousing 406 may be a housing of a portable electronic device. In otherembodiments, the housing 406 may be a rigid housing adapted to containthe rechargeable battery 400.

The photo interrupter may include a phototransmitter portion 408 a and aphotoreceiver portion 408 b. As the rechargeable battery expands, therechargeable battery may physically interrupt the optical path betweenthe phototransmitter 408 a and photoreceiver 408 b. In this manner,interruption of the photo interrupter can indicate the expansion of therechargeable battery. In some examples, the photoreceiver portion 408 bmay be a passive reflective element. In still other embodiments, thephoto interrupter may be positioned to transmit and/or receive lightthrough a through-hole within the rechargeable battery itself. In thismanner, expansion of the rechargeable battery can move or otherwisealter the geometry of the through-hole, which in turn can interrupt thepath of light therethrough.

In another embodiment, the expansion detector 408 may be an acousticresonance sensor positioned in communication with an internal cavity ofa portable electronic device. For example, the acoustic resonance sensormay emit a test pulse of sound from a transmitter 408 a into the cavitydefined between the rechargeable battery 400 and the housing 406 andmonitor, with a receiver 408 b, the acoustic resonance or resonancesignature returned by the cavity. As the rechargeable battery expands,the acoustic resonance of the internal cavity may change. In thismanner, the acoustic resonance sensor can indicate the expansion of therechargeable battery. In some embodiments, the receiver 408 b may beincorporated into the transmitter 408 a.

In another embodiment, the expansion detector 408 may be a gas pressuresensor positioned in communication with a sealed internal cavity of aportable electronic device. The sealed internal cavity may be filledwith any number of suitable gasses. The gas pressure sensor can detectthe pressure of gas within the sealed internal cavity. As therechargeable battery expands, the pressure within the sealed internalcavity may change. In this manner, the gas pressure sensor can indicatethe expansion of the rechargeable battery.

FIG. 5 depicts an example side cross-section of an example rechargeablebattery 500 and an expansion detector 508 disposed within a housing 506.The expansion detector may include one or more physical contactswitches, each made from at least two electrically conductive surfaces508 a, 508 b. For example, a first electrically conductive surface 508 adisposed on an external surface of the rechargeable battery may comeinto physical contact with a second electrically conductive surface 508b upon expansion of the rechargeable battery. For example, the secondelectrically conductive surface 508 b may be disposed on an interiorsurface of the housing 506 of the electronic device. As the rechargeablebattery 500 expands, the first electrically conductive surface 508 a maybecome nearer to the second electrically conductive surface 508 b. Uponsufficient expansion, the first and second electrically conductivesurfaces 508 a, 508 b may contact one another, thereby completing anelectrical circuit. In this manner, the physical contact switch canindicate the expansion of the rechargeable battery.

FIG. 6A depicts an example top plan view of an example rechargeablebattery 600 and a resistive expansion detector 604 disposed on anexterior surface of the rechargeable battery 600. As illustrated in FIG.6A, the rechargeable battery is in an unexpanded state. The resistiveexpansion detector 604 may be formed from two or more interlocking orinterlaced comb patterns 604 a, 604 b. As the rechargeable batteryexpands, the teeth of the combs 604 a, 604 b may slide apart orotherwise separate, which can change the electrical resistance betweenthe one or more interlocking or interlaced combs for example as shown inFIG. 6B. In this manner, the resistance sensor can indicate theexpansion of the rechargeable battery.

FIG. 6C depicts a top plan view of an example rechargeable battery 600and a resistive expansion detector 604 disposed on an exterior surfaceof the rechargeable battery 600. The resistive expansion detector 604may be one or more sacrificial conductive strips configured tomechanically fail under tension. For example, a thin strip 604 a ofelectrically conductive material may be disposed on an external surfaceof the rechargeable battery, such that when the rechargeable batteryexpands a certain amount, the thin strip 604 a may be pulled apart undertension.

As a result of the physical break, the thin strip 604 a may no longerconduct electricity. In this manner, the thin strip 604 a can indicatethe expansion of the rechargeable battery. In some embodiments, asacrificial conductive strip may be directly connected to one or moreterminals of the rechargeable battery such that when the sacrificialstrip breaks, the rechargeable battery is immediately disconnected fromcharging or discharging circuitry. In this manner, the sacrificial stripmay function as a fuse that is triggered by rechargeable batteryexpansion.

In some embodiments, more than one sacrificial conductive strip may beused. For example, each sacrificial strip may be adapted to break apartunder different tension conditions. For example, a first sacrificialstrip 604 a may fail under a first tension and a second sacrificialstrip 604 b may fail under a second tension and a third sacrificialstrip 604 c may fail under a third tension. In this manner, theprogressive failure of a plurality of sacrificial strips may indicatethe progressive expansion of the rechargeable battery.

In still further embodiments, multiple sacrificial strips may bepositioned at regular intervals across the surface of the rechargeablebattery. For example, as shown in FIG. 6D, eleven sacrificial strips 604may be positioned at regular intervals across the surface of therechargeable battery. Each of the sacrificial strips may be electricallycoupled to a pull-up or pull-down resistor such that an interrogator 608may interrogate the resistive expansion detector digitally. In someembodiments, the interrogator 608 may be accessed as a simple memoryregister. For example, as illustrated, each of the multiple sacrificialstrips may be connected to pull-up resistors (not shown) such that theinterrogator 608 interprets each of the still-connected sacrificialstrips 604 as a digital one.

However, upon expansion of the rechargeable battery as shown in FIG. 6E,one or more of the sacrificial strips 604 may break, causing the brokensacrificial strips to be registered by the interrogator 608 as a digitalzero.

FIG. 7 is a flow chart depicting example operations of a method fordetecting rechargeable battery expansion. The method may begin withoperation 702 during which rechargeable battery expansion is detected byany number of suitable means, including the embodiments describedherein. Thereafter, at 704, the detected expansion and/or rate ofexpansion of the rechargeable battery may be compared against a selectedthreshold. For example, slight (or slow) expansion may not necessarilybe a cause for determining that a rechargeable battery is in need ofreconditioning or replacement. Once, at 704, the method determines thatthe expansion of the rechargeable battery (e.g., a dimension of therechargeable battery at the point that expansion is measured) exceedsthe selected expansion threshold, the method may report that therechargeable battery has expanded or swelled at operation 706.

FIG. 8 is a flow chart depicting example operations of a method forcompensating for and arresting rechargeable battery expansion. Themethod may begin at operation 802 in which the method receives anindication that an associated rechargeable battery has expanded.Thereafter, at operation 804, one or more charging and/or dischargingcharacteristics may be modified or changed. For example, if expansion isdetected, the rechargeable battery may be set to charge at a slower rateduring future charging cycles.

FIG. 9 is another flow chart depicting example operations of a methodfor predicting and or inferring rechargeable battery expansion as aresult of rechargeable battery age. The method may begin at operation902 in which the effective or actual age and/or rate of aging of arechargeable battery can be determined. For example, the rechargeablebattery age may be a calendar age of the rechargeable battery, acharge/discharge cycle count associated with the rechargeable battery, arechargeable battery expansion detected by an expansion detector, or anyother suitable means for determining that a rechargeable battery hasexpanded. The rate of aging may be determined from historical datarelating to previous determinations of rechargeable battery age.Thereafter, at 704, the determined age and/or rate of aging of therechargeable battery may be compared against a selected threshold. Ifeither or both the determined age and/or rate of aging exceeds theselected thresholds, the method may report a rechargeable batteryexpansion at operation 906.

FIG. 10 is another flow chart depicting example operations of a methodfor mitigating rechargeable battery expansion over time. The method maybegin at operation 1002 at which an effective target charge capacity canbe determined. The target charge capacity of the battery can bemeasured, determined, estimated, or inferred in any number of suitableways. For example, certain embodiments may infer the target chargecapacity of the rechargeable battery by measuring the resting voltage ofthe battery. In other examples, the target charge capacity of therechargeable battery can be estimated by comparing the rechargeablebattery discharge voltage profile to a rechargeable battery dischargemodel stored in a memory. In other examples, other conventional targetcharge capacity algorithms, circuits, or estimations maybe used.

After the target charge capacity of the rechargeable battery isdetermined, the method may continue to operation 1004 to determinewhether the determined target charge capacity is less than a selectedthreshold. The selected threshold may indicate the next level at which aprocessing unit may adjust power characteristics of the rechargeablebattery.

In the event that operation 1004 determines that the target chargecapacity is less than the selected threshold, the method may continue tooperation 1006 at which the maximum charging voltage used to charge therechargeable battery may be reduced by a selected amount. For example,in some embodiments, the maximum charging voltage may be reduced by anamount proportional to the change in the expected and/or target chargecapacity. More particularly, if the target charge capacity drops by 10%,the maximum charging voltage may be reduced by 1.0%. In other examples,the maximum charging voltage can be reduced at fixed or variableintervals in response to drops in the target charge capacity. Forexample, if the target charge capacity drops by 10%, the maximumcharging voltage may be reduced by 50 mV. In other examples, othervoltage drop intervals may be used.

FIG. 11 is another flow chart depicting example operations of a methodfor predicting and or inferring rechargeable battery expansion as aresult of rechargeable battery age. The method may begin at operation1102 which can determine whether a rechargeable battery is expanded.Next, operation 1104 can determine whether the expansion exceeds aselected threshold. If the expansion exceeds a selected threshold, themethod may continue to operation 1106 that can provide a report that thebattery is expanded. Thereafter, the expansion threshold used inoperation 1104 may be adjusted at operation 1108.

These and other methods described herein may report rechargeable batteryexpansion to a processing unit associated with the portable electronicdevice powered by the rechargeable battery. After receiving theexpansion signal the processing unit can respond in any number of ways,regardless whether the signal is derived from an objective measurementof the physical dimensions of the rechargeable battery or whether thesignal is derived from an estimation of expected rechargeable batteryexpansion based on rechargeable battery age or heath.

In the present disclosure, various embodiments relating to systems andmethods for detecting and compensating for battery expansion over timeare described. However, one may appreciate that each of theseembodiments may also apply to monitor for battery contraction over time.

In the present disclosure, the methods disclosed may be implemented assets of instructions or software readable by a device. Further, it isunderstood that the specific order or hierarchy of steps in the methodsdisclosed are examples of sample approaches. In other embodiments, thespecific order or hierarchy of steps in the method can be rearrangedwhile remaining within the disclosed subject matter. The accompanyingmethod claims present elements of the various steps in a sample order,and are not necessarily meant to be limited to the specific order orhierarchy presented.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not target to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings.

We claim:
 1. An electronic device, comprising: a rechargeable batterywithin a housing; a processing unit configured to control an electricalinput generated by a power source and provided to the rechargeablebattery; and an expansion detector electrically coupled to theprocessing unit and comprising a capacitive sensor; wherein: theexpansion detector sends an expansion signal to the processing unit upondetermining that the rechargeable battery has expanded; and in responseto receiving the expansion signal, the processing unit modifies one ormore characteristics of the electrical input.
 2. The electronic deviceof claim 1, wherein the capacitive sensor comprises: a firstelectrically conductive surface coupled to an external surface of therechargeable battery; and a second electrically conductive surfaceconductively coupled to the first electrically conductive surface. 3.The electronic device of claim 2, wherein the expansion detector isconfigured to measure a capacitance between the first electricallyconductive surface and the second electrically conductive surface. 4.The electronic device of claim 2, wherein the second electricallyconductive surface is coupled to the housing.
 5. The electronic deviceof claim 2, wherein the second electrically conductive surface comprisesa top surface of the rechargeable battery; and the external surface ofthe rechargeable battery comprises a bottom surface of the rechargeablebattery.
 6. The electronic device of claim 1, wherein the capacitivesensor comprises: an array of electrically conductive surfaces, each ofwhich is coupled to an external surface of the rechargeable battery. 7.The electronic device of claim 6, wherein the expansion detector isconfigured to individually measure a capacitance between eachelectrically conductive surface of the array of electrically conductivesurfaces and a reference surface.
 8. The electronic device of claim 1,wherein: the expansion detector comprises a first electricallyconductive plate and a second electrically conductive plate separated byan air gap; the first electrically conductive plate is coupled to aninternal surface of the housing; and the second electrically conductiveplate is coupled to an external surface of the housing.
 9. Theelectronic device of claim 8, wherein the expansion detector isconfigured to send the expansion signal to the processing unit upondetecting an electrical connection between the first electricallyconductive plate and the second electrically conductive plate.
 10. Arechargeable battery within a housing of a portable electronic device,the rechargeable battery comprising: a rechargeable battery module; acontainer containing the rechargeable battery module; and a rechargeablebattery expansion detector electrically coupled to a processing unitassociated with the portable electronic device, the rechargeable batteryexpansion detector comprising a capacitive sensor; wherein: therechargeable battery expansion detector sends an expansion signal to theprocessing unit upon determining that the rechargeable battery hasexpanded; and in response to receiving the expansion signal, theprocessing unit modifies one or more characteristics of an electricalinput to the rechargeable battery.
 11. The rechargeable battery of claim10, wherein the capacitive sensor comprises: a first electricallyconductive surface; and a second electrically conductive surface;wherein the first electrically conductive surface is coupled to anexternal surface of the rechargeable battery.
 12. The rechargeablebattery of claim 11, wherein the rechargeable battery expansion detectoris configured to measure a capacitance between the first electricallyconductive surface and the second electrically conductive surface. 13.The rechargeable battery of claim 10, wherein the capacitive sensorcomprises: an array of electrically conductive surfaces, wherein eachelectrically conductive surface of the array of electrically conductivesurfaces is coupled to an external surface of the rechargeable battery.14. The rechargeable battery of claim 11, wherein the secondelectrically conductive surface is coupled to the housing.
 15. Therechargeable battery of claim 13, wherein: the array of electricallyconductive surfaces is a first array of electrically conductive surfacescoupled to a top surface of the rechargeable battery; and the capacitivesensor further comprises a second array of electrically conductivesurfaces coupled to a bottom surface of the rechargeable battery. 16.The rechargeable battery of claim 15, wherein the rechargeable batteryexpansion detector is configured to measure a capacitance between one ofthe first array of electrically conductive surfaces and one of thesecond array of electrically conductive surfaces.
 17. The rechargeablebattery of claim 13, wherein the rechargeable battery expansion detectoris configured to individually measure a capacitance between eachelectrically conductive surface of the array of electrically conductivesurfaces and a reference surface.
 18. The rechargeable battery of claim10, wherein: the rechargeable battery expansion detector comprises afirst electrically conductive plate and a second electrically conductiveplate separated by an air gap; the first electrically conductive plateis coupled to an internal surface of the housing; and the secondelectrically conductive plate is coupled to an external surface of thehousing.
 19. The rechargeable battery of claim 18, wherein therechargeable battery expansion detector is configured to send theexpansion signal to the processing unit upon detecting an electricalconnection between the first electrically conductive plate and thesecond electrically conductive plate.
 20. The electronic device of claim1, wherein the capacitive sensor comprises: a first electricallyconductive surface coupled to an external surface of the rechargeablebattery; a second electrically conductive surface; and an insulatorcoupled to and separating the first electrically conductive surface andthe second electrically conductive surface.
 21. The electronic device ofclaim 20, wherein the insulator comprises a cell of the rechargeablebattery.
 22. The electronic device of claim 20, wherein the secondelectrically conductive surface is within the rechargeable battery.